Sounding-board for pianos



(No Model.) 2 VSheets-Sheet 1.

G. GADDIGK.

SOUNDING BOARD EUR PIANQS.

N0.29s,414. Patentedeb. 12-1884.

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(No Mdel.) sheets-sheet 2.

G. CA-DDICK SOUNDING BOARD POR PIANOS. 4

No. 293,414. Patented Feb. 12,1884.

UNTTED STATES PATENT @Errea GEORGE CADDICK, OF ALLEGHENY, PENNSYLVANIA.

SOUNDlNG-BOARD FOR PlANOS.

SPECIFICATION forming part of Letters Patent N0. 293,414, dated February 12, 1884.

(No model.)

@ til whom t may conce/zu,.-

Be it known that I, GEORGE CADDICK, of Allegheny, Pennsylvania, have invented certain new and useful Improvements in Sounding-Boards for Grand and Upright Pianos, 0l' which the i'ollowing is aspeciication, reference being had to the accompanying drawings.

The invention relates to upright pianos; and it consists in a double sound-board composed of back and belly sound-boards united at their side edges by walls and forming a soundingchamber, said sound-boards being sprung into an arched or crowning form by means of sound-posts extending from the ribs of one sound-board to the other, said chamber having apertures or holes to emit the sound. This sound-chamber is covered with a full iron l'rame, which may be made to any desired scale and pat-tern.

The novelty consists in springing the belly sound-board and at the same time bowing the back sound-board by ineansof the posts introduced between them, thus producing two elastic sound-boards.

Figure l is a plan viewof a device embodying my invention. AFig. 2 is a longitudinal section of the same. Figs. 3 and et represent, respectively, transverse and vertical sections of the two sound-boards arranged one on each side of the back framing of the piano.

A in the accompanying drawings is the back frame of the piano, constructed, in the usual way, to any desired pattern. To the inner side of the back frame one-inch pieces of board B C are glued to the top, sides, and bottom. On the one-inch pieces of board is glued the back sound-board, G, having previously been made the required thickness, (the fiber of both the sound-boards to run perpendicula-rlywhen placed in the instrumenu) and provided with ribs M, placed at right angles to the ber of the sound-board. The ribs are `set at equal distances apart, so that the sound-posts, when glued onto the ribs of the back sound-board, will come immediately under the ribs of the belly sound-board, arranged either in rows or in a direct line beneath the bridges, (if in rows, it will take from sixteen to twenty soundposts,) the sound-posts to be of such a heightA that when the belly sound-board H is sprung over them the back sound-board will bow about one-fourth of an inch in the center and leave the belly sound-board sprung in the center also about one-fourth of an inch. The soundposts around the outer edge of the soundboardgshould be about'jfone-iburth of an inch higher than the space between the ribs ofthe two sound-boards, aud thc sound-post in the center about one-haltl inch higher than the space between the ribs of the two soundboards, so that the sound-boards will bow evenly from the sides and ends to the center. D and E are two planks, two and a halt' or three inches thick, equal to the width between the two sound-boards. These planks are glued to the inner side ofthe back sound-board, G. On the plank-pieceD is glued the belly soundboard H and the wrest-plank J. The belly sound-board, being provided with bridges L, is sprung over the sound-posts for their equivalents, and then glued to the lower plank-piece, I. The bridge L is to beplaned orf in the middle, so that it will b e level on the top and project above the plane of the full iron frame K enough to give a proper bearingto the strings and to suliciently compress the belly soundboardqsay about one-sixteenth of an inch.

The iron frame K may be made to suit any scale, and to any desired pattern,and is firmly put on over the sound-chamber formed by the sound-boards Gr and H. There economy in space is required inthe depth of the piano,the sound-boards may be put on each side of the back frame, leaving the back frame inside and between the back and belly sound-boards. According to this arrangement the back soundboard will be glued to a strip that is glued at the top, bottom, and sides, on the outside or back ,of the back frame. The sound-posts are glued in such places as will not come in contact or interfere with the back frame. The belly sound-board is then glued to the wrestplank, which in turn is glued to the inner side or front of the back l'rame, after which the belly sound-board is sprung over the soundposts and glued to the top, bottom, and sides of the back frame. rlhe bridges are then tted onto the belly sound-board and the iron frame put on, as previously described. A screw-press may be made that would-spring the belly sound-board over the sound-posts and glue it down at the same time,thus facilitating the springing process. This arrangement of sound-boards-one on each side of the ICO back framing-may be applied to grand pianos. It is the most practicable Way, and the upright piano so constructed will remain longer in tune. Figs. 3 and 4 in drawings represent, respectively, transverse and vertical sections of an upright-piano framing and sound-board*arranged in this Way. It will be remembered that the back sound-board is glued on iiat, and is only bowed by the force employed in springing the belly sound-board over the sound-posts and by the pressure of the string on the bridges. At the time when the belly sound-board is about tobe sprung over the sound-posts the tops of the soundposts may be touched with glue, so that the sound-posts will be glued to the ribs of the belly sound-board, as well as to the ribs of the back sound-board, to prevent any rattle or jarring ever occurring.

To persons skilled in the art of piano-manufacturing I will explain my present mode of construction upon the theory of sound and its propagation. My improvement is the result of many experiments, including the construction of three experimental pianos.

Sound is produced by the vibration of elastic bodies. In many cases the elasticity of a body can bc augmented by producing a closer aggregation of the molecules. Some metals are rendered more elastic by hammering them cold. Steel acquires a greater elasticity by tempering, and wood is rendered more elastic bythe compression or distention of its fibers. In accordance with this theory, the object to be attained, then, is to put the sound-boards in a condition of elasticity and keep them so,

which is done by springing the belly soundboard over the sound-posts, thus distending the ibenwhile the fibers of the baclr sound-board are distended by the pressure brought to bear on it by springing the belly sound-board over the sound-posts and by the pressure of the strings on the bridges. Heretofore in the construction of pianos With one sound-board the objection has been that the sound-board, being exposed to varying temperatures and atmospheres, has soon lost its curvature and elasticity, and hence arises the chief cause Why pianos so soon depreciate in tone. In my double sound-board it has been my object to preserve the curvature, elasticity,and sonorousness as long as possible. By this method of springing the sound-boards over soundposts all pull-over from the Wrest-plank is prevented, the back sound-board acting as a stay or brace to it. The strings can take a more solid bearing on the bridges, as sinking of the sound-boards cannot occur, for the soundboards support and re-enforce each other.

I am aware that pianos with double soundboards connected by sound-posts are old, and such are not broadly claimed; but

Vhat I claim, and desire to secure by Ilettcrs Patent as my invention, is-

In a piano, the double sound-board composed of the two sound-boards, one in front of the back framing, 'the other in rear of it, said boards being sprung into an arched or crowning form by means of sound-posts introduced between them, substantially as specified.

-In testimony that I claim the foregoing iinprovements in upright pianos, as above described, I have hereunto set my hand this 16th day of February, 1882.

GEORGE CADDICK.

Vitnesses:

J. J. McCoRMrcK, LEDLIE GLOUINGER. 

